[IMPALA-9905] Allow runtime scalar subquery check when group by clause is present

• Type: Improvement
• Status: Resolved
• Priority: Minor
• Resolution: Fixed
• Component/s: Frontend
• Labels: planner tpc-ds
• Epic Link: Subquery Support
• Target Version: Impala 4.0.0
• Epic Color: ghx-label-8
• Assignee: Shant Hovsepian
• Reporter: Shant Hovsepian
• Created: 28/Jun/20 16:53
• Updated: 17/Jul/20 03:54
• Resolved: 17/Jul/20 03:54

Description

We can also use a runtime scalar subquery check for subqueries that have a scalar return type and also contain a grouping expression.

 

For example the following query would pass a runtime scalar check, given the predicate on the grouping expression.

select * from functional.alltypes where id < (select count(bool_col) from functional.alltypes where int_col=1 group by int_col);

 

Ideally we could detect situation like the above at plan time and avoid the runtime scalar check all together with IMPALA-1285

Issue Links

• depends upon: IMPALA-6314 Add run time scalar subquery check for uncorrelated subqueries
• is related to: IMPALA-1285 Subquery with group by and where could realize the result has one row.